Group 10 Metal Benzene-1,2-dithiolate Derivatives ... - ACS Publications

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Group 10 Metal Benzene-1,2-dithiolate Derivatives in the Synthesis of Coordination Polymers Containing Potassium Countercations Oscar Castillo,† Esther Delgado,*,‡ Carlos J. Gómez-García,§ Diego Hernández,‡ Elisa Hernández,‡ Avelino Martín,∥ José I. Martínez,⊥ and Félix Zamora*,‡,# †

Departamento de Química Inorgánica, Universidad del País Vasco, UPV/EHU, Apartado 644, E-48080 Bilbao, Spain Departamento de Química Inorgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain § Instituto de Ciencia Molecular, Departamento de Quı ́mica Inorgánica, Universidad de Valencia, C/Catedrático José Beltrán, 2. 46980 Paterna, Valencia, Spain ∥ Departamento de Química Inorgánica, Universidad de Alcalá, Campus Universitario, E-28871 Alcalá de Henares, Spain ⊥ Departamento de Nanoestructuras, Superficies, Recubrimientos y Astrofísica Molecular, Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), 28049 Madrid, Spain # Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain

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‡

S Supporting Information *

ABSTRACT: The use of theoretical calculations has allowed us to predict the coordination behavior of dithiolene [M(SC6H4S)2]2− (M = Ni, Pd, Pt) entities, giving rise to the first organometallic polymers {[K2(μ-H2O)2][Ni(SC6H4S)2]}n and {[K2(μH2O)2(thf)]2[K2(μ-H2O)2(thf)2][Pd3(SC6H4S)6]}n by one-pot reactions of the corresponding d10 metal salts, 1,2-benzenedithiolene, and KOH. The polymers are based on σ,π interactions between potassium atoms and [M(SC6H4S)2]2− (M = Ni, Pd) entities. In contrast, only σ interactions are observed when the analogous platinum derivative is used instead, yielding the coordination polymer {[K2(μ-thf)2][Pt(SC6H4S)2]}n.

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doping, and redox behavior have been reported.28 On the other hand, we have recently reported29 the synthesis, structural characterization, and magnetic and electrical properties of the 1D- and 2D-CP forms of {[K2(μ-H2O)2(μ-thf)(thf)2][M(SC6H2Cl2S)2]}n (M = Ni, Pd), {[K2(μ-H2O)2(thf)6][Pt( S C 6 H 2 Cl 2 S) 2 ]} n , a nd {[ K 2 (μ -H 2 O)(μ- t h f ) 2 ]] [Pt(SC6H2Cl2S)2]}n. These studies have confirmed that the presence of donor substituents in the aromatic ring of the dithiolene ligands favors the linkage of group 1 metal countercations to the group 10 metal dithiolene anionic entities by σ interactions, yielding CPs. On the other hand, some examples of organometallic polymers of alkali metals, mainly potassium, showing π interactions to aromatic rings have been described.30−33 However, as far as we know, the compound [K2Fe(SC6H5)4]n34 is the only example of an organometallic polymer made up with transition metal aromatic thiolate entities linked by alkali complexes through σ and π interactions. Our previous studies29 confirmed the coordination of potassium centers to [M(S2C6H2Cl2)2]2− (S2C6H2Cl2 = 1,4dichlorobenzenedithiolate; M = Ni, Pd, Pt) entities via K−S and

INTRODUCTION For a long time, the chemistry of transition metals with dithiolene ligands has been a research field of high interest.1,2 Among other reasons, some of the main driving forces focusing attention on these compounds are their outstanding electronic properties, such as magnetism and/or electrical conductivity, and the wide structural diversity that these compounds have shown.3−17 However, despite the fact that many d10 metal dithiolene derivatives forming discrete molecules or supramolecular networks have been widely described,18−21 little is still known about dithiolene-based coordination polymers (CPs). Indeed, some of the examples giving rise to CPs are [Na(N15C5)2]2[M(i-mnt)2] (M = Pt,22 Pd;23 i-mnt = 1,1dicyanoethylene-2,2-dithiolate; N15C5 = 2,3-naphtho-15crown-5), [K(DC18C6-A)]2[M(mnt)2],24 (M = Ni, Pd, Pt; mnt = 1,2-dicyanoethylene-1,2-dithiolate; DC18C6-A = dicyclohexyl-18-crown-6 isomer A), [K(DC18C6-A)] 2 [Pt(imnt)2],25 [{Na(benzo-15-crown-5)}2Ni(i-mnt)2]n·nCH2Cl2,26 [{CuL} 2 Gd(O 2 NO){Ni(mnt) 2 }] n ·CH 3 OH·CH 3 CN, and [{CuL} 2 Sm(O2 NO){Ni(mnt) 2 }] n·2CH 3 CN] (L = N,N′propylenebis(3-methoxysalicylideneiminato)).27 Additionally, a microporous framework, Cu[Ni(pdt)2] (pdt2− = pyrazine- 2,3-dithiolate), showing electrical conductivity, © 2017 American Chemical Society

Received: July 16, 2017 Published: September 18, 2017 11810

DOI: 10.1021/acs.inorgchem.7b01775 Inorg. Chem. 2017, 56, 11810−11818

Article

Inorganic Chemistry Table 1. Crystallographic Data and Structure Refinement Details of Compounds 1−3 formula M T (K) λ (Å) cryst syst space group a (Å) b (Å) c (Å) α (deg) β (deg) γ (deg) V (Å3) Z ρcalcd (g cm−3) μ (mm−1) F(000) reflections collected unique data/parameters Rint no. of rflns (I > 2σ(I)) goodness of fit (S)a R1b/wR2c (I > 2σ(I)) R1b/wR2c (all data) largest diff peak/hole (e Å−3)

1

2

3

C12H12K2NiO2S4 453.37 200(2) 0.71073 monoclinic P21/n 6.9977(4) 19.160(1) 7.1060(6)

C52H68K6O10Pd3S12 1791.58 200(2) 0.71073 triclinic P1̅ 11.8802(4) 12.2975(9) 14.311(2) 101.661(8) 98.624(6) 116.546(7) 1761.5(3) 1 1.689 1.517 904 38360 8066/382 0.068 5612 1.122 0.0457/0.0948 0.0869/0.1163 2.144/-1.163

C20H24K2O2PtS4 697.92 200(2) 0.71073 orthorhombic Pnma 13.8768(2) 25.1331(4) 7.3964(3)

111.093(7) 888.9(1) 2 1.694 2.027 460 19946 2037/97 0.118 1367 1.296 0.0568/0.1235 0.1073/0.1522 1.265/-0.668

2579.6(1) 4 1.797 6.100 1360 23195 2978/136 0.094 2338 1.070 0.0448/0.0958 0.0678/0.1110 2.743/-2.534

a S = [∑w(Fo2 − Fc2)2/(Nobs − Nparam)]1/2. bR1 = ∑||Fo|−|Fc||/∑|Fo|. cwR2 = [∑w(Fo2 − Fc2)2/∑wFo2]1/2; w = 1/[σ2(Fo2) + (aP)2 + bP], where P = (max(Fo2,0) + 2Fc2)/3 with a = 0.0596 (compound 1), a = 0.0363 (compound 2), a = 0.0419 (compound 3), b = 3.5289 (compound 1), b = 5.4711 (compound 2), and b = 16.0296 (compound 3).

ohmic conductors. The cooling and warming rates were 1 K min−1 in all cases. Magnetic measurements were performed with a Quantum Design MPMS-XL-5 SQUID magnetometer in the temperature range 2−300 K with a magnetic field of 0.5 T on polycrystalline samples of compounds 1−3, all immersed in their mother liquor (with dry masses of 14.97, 15.64, and 19.31 mg, respectively). Susceptibility data were corrected for the sample holder and solvents for the diamagnetic contribution of the salts using Pascal’s constants.35 Crystal Structure Determination of Complexes 1−3. Single crystals of compounds 1−3 were covered with a layer of a viscous perfluoropolyether (FomblinY), mounted on a cryoloop with the aid of a microscope, and immediately placed in the low-temperature nitrogen stream of the diffractometer. The intensity data sets were collected at 200 K on a Bruker-Nonius KappaCCD diffractometer equipped with an Oxford Cryostream 700 unit. The structures were solved, with the WINGX package,36 by direct methods (SHELXS-2013)37,38 and refined by least squares against F2 (SHELXL-2014).38 All hydrogen atoms were positioned geometrically and refined by using a riding model. All nonhydrogen atoms were refined anisotropically. Table 1 collects crystallographic data and structure refinement details of 1−3. Compound 2 presented disorder in the O5, C71, C72, C73, and C74 atoms of the tetrahydrofuran molecule. By using the corresponding Shelxl PART commands37−39 and FVAR variables, two positions were refined with 56% and 44% occupancies, respectively. Synthesis of {[K2(μ-H2O)2][Ni(SC6H4S)2]}n (1). HSC6H4SH (181 mg, 1.27 mmol) was added to 10 mL of a 5% aqueous solution of KOH. Then, a solution of NiCl2·6H2O (150 mg, 0.63 mmol) in 10 mL of EtOH/H2O (1/1) was slowly added. The mixture was stirred for 30 min, and then the solvent was removed under vacuum, yielding a solid residue which was washed with n-hexane and extracted with THF. Crystallization of the solid in wet THF/n-heptane (1/1) at room temperature yielded crystals suitable for X-ray analysis of compound 1 (125 mg, 43.76%). Anal. Calcd (found) for C12H12K2NiO2S4: C, 31.79 (37.96); H, 2.67 (4.20); S, 28.29 (26.46).

K−Cl bonds. Probably, the presence of chloride substituents in the benzene ring hampers the coordination to the aromatic carbons of this group and the formation of organometallic polymers. Herein we report how theoretical calculations may serve as a tool for the structural design of organometallic polymers based on the coordination capabilities of [M(SC6H4S)2]2− (SC6H4S = benzenedithiolate; M = Ni, Pd, Pt) entities. We also present the synthesis, characterization, and physical properties of the first reported alkali metal−group 10 metal dithiolene organometallic polymers {[K2(μ-H2O)2][Ni(SC 6 H 4 S) 2 ]} n (1) and {[K 2 (μ-H 2 O) 2 (thf)] 2 [K 2 (μH2O)2(thf)2][Pd3(SC6H4S)6]}n (2) as well as the coordination polymer {[K2(μ-thf)2][Pt(SC6H4S)2]}n (3).

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EXPERIMENTAL SECTION

The syntheses of compounds 1−3 were carried out under an argon atmosphere using degassed solvents. Elemental analyses were performed on an LECO CHNS-932 Elemental Analyzer. The dc electrical conductivity was measured in the temperature range 200−400 K with the two- or four-contact method (depending on the size of the crystals) on several single crystals of compounds 1−3. Crystals of compounds 1−3 were measured in three or four consecutive scans: they were initially cooled from 300 to 200 K (since at lower temperatures the resistance was above the detection limit of our equipment, 5 × 1011 Ω), heated from 200 to 400 K, and then cooled again from 400 to 200 or 300 K. The contacts were made with Pt wires (25 μm diameter) using graphite paste. The samples were measured with a Quantum Design PPMS-9 equipment connected to an external voltage source (Keithley Model 2450 source meter) and amperometer (Keithley Model 6514 electrometer). Since all of the crystals lose crystallinity very quickly, the crystals were covered with paraffin oil immediately after the contacts were made. All the quoted conductivity values have been measured in the voltage range where the crystals are 11811


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Inorganic Chemistry

Figure 1. Computed 3D isosurfaces corresponding to the positive Fukui function f+(r) for the different isolated [M(SC6H4S)2]2− entities: (a) M = Ni; (b) M = Pd; (c) M = Pt. All of the 3D isosurfaces are shown for a value of +0.0005 e− Å−3. Superimposed black circles indicate the most favorable sites to anchor metal centers per unit cell according to the largest value regions of f+(r). Synthesis of {[K 2 (μ-H 2 O) 2 (thf)] 2 [K 2 (μ-H 2 O) 2 (thf) 2 ][Pd3(SC6H4S)6]}n (2). Compound 2 has been obtained by following the same procedure as for compound 1, but using Pd(OAc)2 as the starting material and maintaining the reaction for 3.5 h. Suitable crystals for X-ray diffraction analysis (257 mg, 34.9%) were obtained by crystallization of the solid in a wet solution of THF/n-heptane (1/1) at room temperature. Anal. Calcd (found) for C52H68K6O10Pd3S12: C, 34.86 (34.51); H, 3.83 (3.81); S, 21.48 (22.26). Synthesis of {[K2(μ-thf)2][Pt(SC6H4S)2]}n (3). Compound 3 was obtained by following the same procedure as for compound 2, but using K2PtCl4 instead. Crystallization in wet THF/n-heptane (1/1) at room temperature yielded suitable crystals for X-ray diffraction of 3 (82 mg, 32.64%). Anal. Calcd (found) for C20H24O2S4PtK2: C, 34.42 (29.73); H, 3.47 (3.01); S, 18.38 (15.13). Theoretical Calculations. In order to rationalize these different packing behaviors within each crystal, we have carried out a set of firstprinciples DFT-based calculations. For that purpose we have made use of the concept of the Fukui functions f±(r)40,41 defined as

⎡ ∂ρ(r) ⎤± f ± (r) = ⎢ ⎥ ⎣ ∂N ⎦v

the inner C−C bridge close to the S atoms) and the other on a S−S bridge of the [M(SC6H4S)2] units and (b) in the configuration where both K atoms are located on each S−S available bridge (Figure S3 in the Supporting Information). Some of these computed geometries have not been detected in the experiments (configurations in right-hand column of Figure S3) and have been heuristically constructed “by hand” as a proof of concept to be directly compared with the experimentally evidenced geometries. We have performed full geometrical optimization to minimize the net forces acting on each atom (below 0.1 eV Å−1). These calculations have been carried out by the efficient plane-wave code QUANTUM ESPRESSO.44 The exchange-correlation (XC) effects have been accounted for by using the revised version of the generalized gradient corrected approximation (GGA) of Perdew, Burke, and Ernzerhof (rPBE),45 and RRKJ norm-conserving scalar-relativistic pseudopotentials have been considered to model the ion−electron interaction.46 In these calculations, the Brillouin zones (BZ) were sampled by means of optimal Monkhorst−Pack grids47 guaranteeing a full convergence in energy and electronic density. A perturbative van der Waals (vdW) correction was used to account for long-range interaction and to check the reliability of all structures.48,49

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(1)

RESULTS AND DISCUSSION The first-principles DFT-computed positive Fukui function f+(r) has been used to elucidate sites with enhanced reactivity within [M(SC6H4S)2] or [M(SC6H2Cl2S)2] (M = Ni, Pd, Pt) entities as they accommodate extra electronic charge (up to −2; net charge state with which they act within each crystal). Figure 1 and Figure S1 in the Supporting Information provide 3D isosurfaces of [M(SC6H4S)2]2− and [M(SC6H2Cl2S)2]2−, respectively, corresponding to the Fukui function f+(r) for the different complexes (all with a value of +0.0005 e− Å−3). The f+(r) isosurfaces for [M(SC6H2Cl2S)2]2− (M = Ni, Pd, Pt) show the preferential donor sites located at the S and Cl atoms, while the C-rings are almost deactivated, therefore precluding any metal coordination (Figure S1). This is in agreement with our reported experimental observations.29 Analogous calculations carried out on [M(SC6H4S)2]2− show that for the [Ni(SC6H4S)2]2− and [Pd(SC6H4S)2]2− entities (Figure 1a,b) the most favorable positions to accommodate the excess of electronic charge and coordinate to metal atoms are on the C-rings, close to the inner C−C bond, and on a S−S bridge. In contrast, for [Pt(SC6H4S)2]2− the most favorable position is centered at the two S−S bridges (Figure 1c). Importantly, for [Ni(SC6H4S)2]2− and [Pd(SC6H4S)2]2− f+(r) adopts large values simultaneously by symmetry in both S−S bridges with the possibility to coordinate metal atoms on them. Therefore, these findings indicate that in the case of [Ni(SC6H4S)2]2− and [Pd(SC6H4S)2]2− the carbon atoms of the aromatic rings are not deactivated, suggesting the possibility to form metal-organic polymers by coordination of metal centers to sulfur and/or to the benzene ring. These results prompted us to evaluate the coordination of potassium ions to [M(SC6H4S)2]2− (M = Ni, Pd, Pt). Thus, compounds 1−3 have been prepared, under an argon

which measure the change in the chemical potential as the number of electrons changes from N to N + dN or to N − dN, respectively. In particular, given that the [M(SC6H4S)2] and [M(SC6H2Cl2S)2] units will act with a net charge state of −2 within each crystal, we have used the positive Fukui function f+(r) to elucidate sites with enhanced reactivity within the complexes [M(SC6H4S)2] and [M(SC6H2Cl2S)2] for M = Ni, Pd, Pt as they accommodate extra electronic charge. By construction, f+(r) describes the way in which the electron density ρ(r) changes as the number of electrons in the complex increases from N to N + dN (in this case from 0 for the neutral case toward the accommodation of 2 extra electrons) at constant external potential.40,41 This means that regions where f+(r) is large are able to stabilize an uptake of electronic charge and are reactive toward the anchoring of electron-rich reactant nucleophiles. In practice, the two Fukui functions can be obtained using a finite difference approximation, as the density differences:40,41 f + (r) = ρv , N + 1(r) − ρv , N (r) f − (r) = ρv , N (r) − ρv , N − 1(r)

(2)

We have computed the positive Fukui function f+(r) for the different isolated complexes [M(SC6H4S)2] and [M(SC6H2Cl2S)2] with M = Ni, Pd, Pt (Figure 1 and Figures S1 and S2 in the Supporting Information) on the basis of the electronic charge densities obtained by the GAUSSIAN09 simulation package42 within a quantum-chemistry allelectron B3LYP model accounting for cc-pVQZ basis sets for H, C, S, and Cl and LanL2DZ basis sets for M = Ni, Pd, Pt (details in ref 42). In all of the calculations the most stable electronic spin configuration is the low-spin (LS) state, in which all eight d electrons in the metal atom are paired (S = 0). This is consistent with the well-known four-coordinate [Ni(II)/Pd(II)/Pt(II)]S4 square-planar complexes,43 as is the present case in both the [M(SC6H4S)2] and [M(SC6H2Cl2S)2] configurations. DFT-based calculations have been carried out on the different building blocks (including the K-based ligands) in two different configurations each: (a) in the configuration where the two K atoms per unit cell are located one on a C-ring hollow site (mostly interacting with 11812


Article

Inorganic Chemistry Scheme 1. Schematic Representation of the Reactions Carried Out To Synthesize Compounds 1−3

Figure 2. Details of the potassium coordination environments in compounds 1 (a), 2 (b), and 3 (c).

atmosphere, by addition of a EtOH/H2O solution of NiCl2·

Compounds 1−3 are built-up from nearly planar [M(κ-S,S′-

6H2O, Pd(OAc)2, or K2PtCl4 to an aqueous solution of

SC6H4S)2]2− entities (MII = Ni (1), Pd (2), Pt (3); SC6H4S =

HSC6H4SH and KOH and further crystallization in wet THF/

benzene-1,2-dithiolate) and potassium counterions to balance

n-heptane (Scheme 1).

the charge. The nature of the group 10 metal in the dithiolate 11813


Article

Inorganic Chemistry entities seems to determine the potassium coordination environment (Figure 2). The crystal structure of compound 1 consists of almost planar [Ni(SC6H4S)2]2− entities, acting as metalloligands toward [K2(μ-OH2)2]2+ dinuclear moieties through the sulfur atoms and the benzene ring of the dithiolene, to form neutral sheets (Figure 2a). The mean planes of the benzene-1,2-dihiolate ligands coordinated to the metal center are parallel but slightly displaced by 0.5 Å and present a dihedral angle of 9.6° with respect to the strictly planar NiS4 core. The coordination sphere of the potassium cation is completed by three sulfur atoms from two [Ni(SC6H4S)2]2− entities (K−S 3.32−3.46 Å), two bridging water molecules (K−O 2.71−2.76 Å), and the η6-coordinated benzene ring (K−C 3.40−3.47 Å) from a third [Ni(SC6H4S)2]2− entity in a distorted-octahedral arrangement. Therefore, the benzene-1,2-dithiolate ligands adopt a chelating mode toward nickel but they also coordinate to potassium atoms in such a way that every sulfur atom establishes two (1Ni + 1K) or three (1Ni + 2K) coordination bonds. All of the Ni−S and K−O distances are within the range usually found in the literature (Table 2). The Table 2. Selected Coordination Bond Lengths (Å) for 1a Ni1−S1× 2 Ni1−S2 × 2

2.1778(13) 2.1708(13)

Ni1···K1iv

3.7098(14)

K1−O1 K1−O1i K1−S1i K1−S1ii K1−S2iii K1−C1 K1−C2 K1−C3 K1−C4 K1−C5 K1−C6

2.757(5) 1.970(2) 1.985(2) 3.3172(19) 3.4624(19) 3.459(5) 3.468(5) 3.421(6) 3.401(6) 3.421(7) 3.435(6)

Symmetry codes: (i) −x + 1, −y + 2, −z + 1; (ii) x, y, z − 1; (iii) x + 1, y, z + 1; (iv) x − 1, y, z − 1. a

internal cohesion of the sheet is reinforced by O−H···S hydrogen bonds involving the water molecules. Finally, these sheets are held together by means of edge to face interactions among these benzene rings located at both sides of the Ni/K/S/water central core (Figure 3). Similarly, compound 2 consists of [Pd(SC6H4S)2]2− entities that behave as metalloligands toward K+ cations but now the presence of THF molecules (Figure 2b), although retaining the bidimensional nature of the resulting metal-organic compound, modifies the way in which potassium atoms interact with the benzene-1,2-dithiolate ligands and as a consequence increases the complexity of the crystal structure. Table 3 collects selected bond lengths for 2. Now, two palladium and three potassium metal centers can be crystallographically distinguished. The coordination environment of both palladium atoms is square planar (PdS4) with two benzene-1,2-dithiolate ligands chelating the metal center through their thiolate groups. However, there is a distinctive shape difference between the two [Pd(SC6H4S)2]2−entities: Pd2 is almost planar, whereas Pd1 has a roof shape. The benzene-1,2-dithiolate ligands, although not coplanar, are arranged parallel around Pd2, although with a displacement of 0.68 Å, to provide a nearly planar entity, but the mean planes of the dithiolate ligands around Pd1 form a dihedral angle of 139° between them and 158/161° with respect to the PdS4 core. As in 1, the sulfur atoms of the benzene-1,2-dithiolate

Figure 3. Coordination environment, 2D organometallic nature, and lamellar supramolecular structure of compound 1.

ligands are involved in two (1Pd + 1K) or three (1Pd + 2K) coordination bonds. The crystallographically independent potassium atoms form two different [K2(μ-OH2)2]2+ entities: a symmetric form (K2−K2) and a nonsymmetric form (K1−K3). The K2 atoms in the symmetric dimeric entity present a coordination sphere formed by two oxygen atoms of the two bridging water molecules, one oxygen atom from one terminal THF molecule, and three sulfur atoms from three palladium dithiolenes. The potassium atoms (K1 and K3) in the nonsymmetric dimeric entity present different coordination environments. K1 interacts with a η6-benzene ring, two oxygen atoms from two bridging water molecules, and three sulfur atoms 11814


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Inorganic Chemistry Table 3. Selected Coordination Bond Lengths (Å) for 2a Pd1−S1 Pd1−S2 Pd1−S3 Pd1−S4 Pd2−S5 × 2 Pd2−S6 × 2

2.2965(13) 2.2946(13) 2.3041(12) 2.2986(12) 2.2905(12) 2.2870(12)

K1−O1 K1−O4 K1−S1 K1−S3 K1−S3i K1−C13ii K1−C14ii K1−C15ii K1−C16ii K1−C17ii K1−C18ii

2.711(4) 2.763(4) 3.2860(18) 3.3057(17) 3.2823(16) 3.081(5) 3.194(5) 3.366(5) 3.432(5) 3.340(5) 3.153(5)

K2−O2 K2−O2iii K2−O5/K2−O5′ K2−S2 K2−S3iii K2−S4iii K2−S5

2.709(4) 2.793(5) 2.69(3)/2.73(4) 3.507(2) 3.4511(19) 3.7888(18) 3.2733(16)

Pd1···K1

3.4070(13)

Pd1···K2vi

3.5534(14)

Pd2···K3

3.7176(14)

K3−O1iv K3−O3 K3−O4iv K3−S2 K3−S5 K3−S6v K3−C7iv K3−C8iv K3−C9iv K3−C10iv K3−C11iv K3−C12iv Pd2···K3v

2.735(4) 2.802(5) 2.682(4) 3.2177(17) 3.5454(19) 3.5862(19) 3.960(6) 3.939(6) 3.501(6) 3.500(6) 3.519(6) 3.774(6) 3.7176(14)

Symmetry codes: (i) −x, −y, −z + 1; (ii) x − 1, y − 1, z; (iii) −x + 1, −y + 1, −z + 1; (iv) −x + 1, −y, −z + 1; (v) −x + 2, −y + 1, −z + 1; (vi) −x + 1, −y + 1, −z + 1. a

from two palladium dithiolene entities in a distorted-octahedral geometry. K3 presents a similar coordination environment but includes an additional oxygen atom from a THF molecule that increases its coordination number up to 7. This nonsymmetric dimer creates a quite complex network of coordination bond connections, reinforced by O−H···S hydrogen bonds, that retains the 2D nature of the resulting structure (Figure 4). However, it substantially modifies the external surface, as now the THF molecules are also present, avoiding the edge to face aromatic interactions observed in compound 1. Therefore, the sheets are only held together by means of weak van der Waals interactions. As far as we know, compounds 1 and 2 are the first examples of alkali metal−group 10 metal dithiolene organometallic polymers. The structure of {[K2(μ-thf)2][Pt(SC6H4S)2]}n (3) consists of a 2D-CP (Figure 2c) in which the platinum centers in the [Pt(SC6H4S)2]2− entities show a square-planar coordination geometry like those observed for compounds 1 (Ni) and 2 (Pd). Table 4 collects the most relevant distances for compound 3. The benzene-1,2-dithiolate ligands are nearly coplanar with a small dihedral angle of 4.6°. The lack of water molecules in the crystal structure forces the THF molecules to adopt the role of bridging ligands in the potassium dimeric entities, [K2(μ-THF)2]2+. The distorted-octahedral geometry around the potassium atoms is completed by the coordination of four sulfur atoms from two dithiolene entities without any evidence of η6 coordination by the benzene groups. Both sulfur atoms of the benzene-1,2-dithiolate ligand are bonded to one platinum and two potassium metal centers. The [Pt(SC6H4S)2]2− entities are perpendicular to the 2D coordination bond network with the benzene rings located at the external surface of the sheet in addition to the THF molecules. The latter avoids the presence of strong supramolecular interactions among the sheets that are only sustained by weak van der Waals interactions (Figure 5). The potassium coordination environments observed for these crystal structures are consistent with the theoretical predictions. Meanwhile in compounds 1 and 2, the K atoms are located simultaneously on a C-ring hollow site and on a S−S bridge of the [M(SC6H4S)2]2− units (in 2 the K2 atom coordinates to the sulfur atom, completing its coordination environment with other oxygen donor ligands); for the Pt compound the K cations are located only on the S−S bridges, in agreement with the calculations that showed large f+(r) values on both S−S bridges. However, given the equilibrium K−K distance within the crystals, the K atoms would not fit in this symmetric

Figure 4. Details on the [Pd(SC6H4S)2]2− (a) [K2(μ-OH2)2]2+ and (b) entities present in compound 2. (c) 2D metal-organic coordination polymer and crystal packing. 11815


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Inorganic Chemistry Table 4. Selected Coordination Bond Lengths (Å) for 3a Pt1−S1 × 2 Pt1−S2 × 2

2.2984(17) 2.2989(17)

Pt1···K1iii

3.625(2)

K1−O1 × 2 K1−S1 × 2 K1−S2i × 2 K2−O1ii × 2 K2−S1 × 2 K2−S2ii × 2 Pt1···K2iv

reveal that the Ni (Figure S3a) and Pd (Figure S3b) compounds are more stable by 0.74 and 1.03 eV per unit cell in the configurations they adopt in the crystal. The Pt compound is also more stable by 0.61 eV per unit cell in the observed configuration (Figure S3c). Therefore, DFT-based calculations allow us to justify by both electronic and energetic considerations the packing configurations adopted by the building blocks within the different Ni, Pd, and Pt crystals. Despite a priori one could consider that all the configurations could be similar for the three [M(SC6H4S)2]2− entities, due to their similar electronic external configurations, slight differences in atomic size and orbital distribution in the metal atoms lead to form essentially different orbital hybridizations and change the packing arrangement from one compound to another. Finally, the presence of the dithiolene complexes acting as metalloligands and the unusual structures found for 1−3 prompted us to evaluate their fundamental electronic properties. Thus, magnetic susceptibility measurements confirmed their expected diamagnetic features. Additionally, dc electrical conductivity measurements (Figures S5 and S6 in the Supporting Information) showed that crystals of 1−3 are semiconductors with room-temperature conductivities in the range of 6 × 10−9 to 6 × 10−7 S cm−1 and activation energies of ca. 710−740 meV (Table S1 and Section S2 in the Supporting Information for experimental details). In all cases the similar electrical conductivities and activation energies can be attributed to the presence of similar pathways for the electron delocalization implying the M−dithiolene units and the K−S and K−O interactions. The complexity of the possible delocalization pathways and the similarity of the conductivity values observed in the three samples preclude any correlation between the structure and the electrical conductivity, which is evinced by the computed density of states profiles as a function of the energy for the Ni, Pd, and Pt compounds (Figure S4 in the Supporting Information) All three crystals exhibit a canonical wide band gap behavior with energy gap values between the valence and conduction bands of 1.32, 1.65, and 2.27 eV for the Ni, Pd, and Pt cases, respectively. These calculated large band gaps agree with the experimental low conductivities measured and the high activation energies obtained. Interestingly, no significant morphological similarities are found between the three density of state profiles, indicating the lack of any correlation between the geometrical and electronic structures in these compounds, as mentioned earlier. Furthermore, we have observed that most crystals show a rapid degradation when they are submitted to low pressure and, therefore, the measured values might be lower that the real values.

2.750(6) 3.343(3) 3.187(3) 2.790(6) 3.193(3) 3.305(3) 3.536(2)

Symmetry codes: (i) x + 1/2, −y + 1/2, −z + 1/2; (ii) x, y, z − 1; (iii) x − 1/2, y, −z + 1/2; (iv) x, y, z + 1.

a

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Figure 5. View of the coordination environments, representation of the 2D coordination polymer network, and lamellar supramolecular structure of compound 3.

CONCLUSIONS

Theoretical calculations have been successfully used to predict coordination capabilities of the [M(SC6H4S)2]2− (M = Ni, Pd, Pt) entities and evaluate their potential to produce novel organometallic polymers containing metalodithiolenes. These are the first examples of alkali metal−group 10 metal dithiolene organometallic polymers. This work provides a clear example of the importance of theoretical tools for the structural design and prediction of physical properties.

configuration because the K−K distance would be too short in the Ni compound and too large in the Pd compound. In contrast, [Pt(SC6H4S)2]2− can nicely accommodate both K atoms on the two S−S bridges. To further understand this interesting behavior, DFT-based calculations have been carried out using the two different configurations found in the [M(SC6H4S)2]2− crystals (Figure S3 in the Supporting Information). The result of these calculations 11816


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Inorganic Chemistry

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Synthesis, Electronic Properties and Applications. Coord. Chem. Rev. 2010, 254, 1457−1467. (12) Alvarez, S.; Vicente, R.; Hoffmann, R. Dimerization and Stacking in Transition-metal Bisdithiolenes and Tetrathiolates. J. Am. Chem. Soc. 1985, 107, 6253−6277. (13) Takaishi, S.; Hosoda, M.; Kajiwara, T.; Miyasaka, H.; Yamashita, M.; Nakanishi, Y.; Kitagawa, Y.; Yamaguchi, K.; Kobayashi, A.; Kitagawa, H. Electroconductive Porous Coordination Polymer Cu[Cu(Pdt)2] Composed of Donor and Acceptor Building Units. Inorg. Chem. 2009, 48, 9048−9050. (14) Ribas, X.; Dias, J. C.; Morgado, J.; Wusrt, K.; Santos, I. C.; Almeida, M.; Vidal-Gancedo, J.; Veciana, J.; Rovira, C. Alkaline SideCoordination Strategy for the Design of Nickel(II) and Nickel(III) Bis(1,2-Diselenolene) Complex Based Materials. Inorg. Chem. 2004, 43, 3631−3641. (15) Llusar, R.; Uriel, S.; Vicent, C.; Clemente-Juan, J.; Coronado, E.; Gómez-García, C. J.; Braïda, B.; Canadell, E. Single-Component Magnetic Conductors Based on Mo3S7 Trinuclear Clusters with Outer Dithiolate Ligands. J. Am. Chem. Soc. 2004, 126, 12076−12083. (16) Llusar, R.; Triguero, S.; Polo, V.; Vicent, C.; Gómez-García, C. J.; Jeannin, O.; Fourmigué, M. Trinuclear Mo3S7 Clusters Coordinated to Dithiolate or Diselenolate Ligands and their use in the Preparation of Magnetic Single Component Molecular Conductors. Inorg. Chem. 2008, 47, 9400−9409. (17) Gushchin, A. L.; Llusar, R.; Vicent, C.; Abramov, P. A.; GómezGarcia, C. J. Mo3Q7 (Q = S, Se) Clusters Containing Dithiolate/ Diselenolate Ligands: Synthesis, Structures, and their use as Precursors of Magnetic Single-Component Molecular Conductors. Eur. J. Inorg. Chem. 2013, 2013, 2615−2622. (18) Machata, P.; Herich, P.; Luspai, K.; Bucinsky, L.; Soralova, S.; Breza, M.; Kozisek, J.; Rapta, P. Redox Reactions of Nickel, Copper, and Cobalt Complexes with “Noninnocent” Dithiolate Ligands: Combined in Situ Spectroelectrochemical and Theoretical Study. Organometallics 2014, 33, 4846−4859. (19) Gao, X. K.; Dou, J. M.; Dong, F. Y.; Li, D. C.; Wang, D. Q. Synthesis, Crystal Structure and Electrochemical Properties of 2D Network Complex {[K(N18C6)]2(CH3CN)}[Ni(mnt)2] with N18C6 = 2,3-Naphtho-18-Crown-6. J. Inorg. Organomet. Polym. 2004, 14, 227− 237. (20) Neves, A. I. S.; Santos, I. C.; Pereira, L. C. J.; Rovira, C.; Ruiz, E.; Belo, D.; Almeida, M. Ni-2,3-Thiophenedithiolate Anions in New Architectures: An in-Line Mixed-Valence Ni Dithiolene (Ni4−S12) Cluster. Eur. J. Inorg. Chem. 2011, 2011, 4807−4815. (21) Dong, F. Y.; Dou, J. M.; Li, D. C.; Gao, X. K.; Wang, D. Q. TwoDimensional Structural Topology Involving Pt/K and K/S Weak Interactions: Complex of Cis−anti−cis-Dicyclohexyl-18-Crown-6 with K2mnt and K2PtCl4. J. Mol. Struct. 2005, 738, 79−84. (22) Gao, X. K.; Dou, J. M.; Li, D. C.; Dong, F. Y.; Wang, D. Q. Synthesis, Crystal Structure and Spectral Analysis of Crown Ether Platinum Bis(Dithiolate) Complexes [Na(N15C5)2]2[Pt(mnt)2] and [Na(N15C5)]2[Pt(i-mnt)2]. J. Mol. Struct. 2005, 733, 181−186. (23) Gao, X. K.; Dou, J. M.; Li, D. C.; Dong, F. Y.; Wang, D. Q. Synthesis and Crystal Structures of Group 10 Metal Bis(Dithiolate) Complexes Constructed by 2,3-Naphtho-15-Crown-5 Or 2,3-Naphtho18-Crown-6. J. Inclusion Phenom. Mol. Recognit. Chem. 2005, 53, 111− 119. (24) Dong, F. Y.; Dou, J. M.; Li, D. C.; Gao, X. K.; Wang, D. Q. Synthesis, Characterization and Properties of One-Dimensional Complexes of Cis-Syn-Cis-Dicyclohexyl-18-Crown-6 with K2[M(mnt)2] (M = Ni, Pd, Pt). J. Inorg. Organomet. Polym. Mater. 2005, 15, 231−237. (25) Sun, Y. M.; Dong, F. Y.; Dou, J. M.; Li, D. C.; Gao, X. K.; Wang, D. Q. Synthesis, Characterization and Thermogravimetric Analysis of Two Dicyclohexyl-18-Crown-6 Pd, Pt Isomaleonitriledithiolate Complexes. J. Inorg. Organomet. Polym. Mater. 2006, 16, 61−67. (26) Long, D. L.; Cui, Y.; Chen, J. T.; Cheng, W. D.; Huang, J. S. OneDimensional Coordination Polymers Formed by Crown Ether Metal Cation Bridges] Synthesis and Crystal Structure of Nickel(II) Dithiolene Complexes [{Na-Benzo-15-Crown-5)} 2 Ni(i-

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.7b01775. Additional information on theoretical studies and physical properties (PDF) Accession Codes

CCDC 1551942−1551944 contain the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by emailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44 1223 336033.

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AUTHOR INFORMATION

Corresponding Authors

*E-mail for E.D.: [email protected]. *E-mail for F.Z.: [email protected]. ORCID

Carlos J. Gómez-García: 0000-0002-0015-577X Félix Zamora: 0000-0001-7529-5120 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS This work was supported in part by the MICINN (grants MAT2016-77608-C3-1-P and MAT2016-75883-C2-1-P), Generalitat Valenciana (PrometeoII/2014/076), and ISIC. J.I.M. acknowledges financial support by the “Ramón y Cajal” Program of MINECO (RYC-2015-17730).

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REFERENCES

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